Method of impregnating wood



May 5, 1936- JIR. cooLlDGE ET AL 2,039,393

METHOD OF IMPREGNATING WOOD Filed May ll, 1932 3 Sheets-Sheet 1 Sigg.' y

,May 5, .1936... J. R. cooLlDGE ET AL METHOD OF IMPREGNATING WOOD Filed May ll, 1932 3 Sheets-Sheet 2 May 5, 193,6- J. R. cooLlDGE; ET AL METHOD OF MPRIEGNAT'NCT WOOD Filed May ll, 1932 3 Sheets-Sheet 3 into the cylinder on a- Patented' May 5, 1936 UNITED STATES PATENT OFFICE McCready, Newton, Mass.; signor to said Coolidge said McCready asappileeaen Mey 11, 1932,v serial No. 610,721- 3 clanes. (ci. 21-.1zi

This invention relates to the impregnation of wood and articles made of wood, or similar materials which can be impregnated by essentially the same methods, for the purpose of preserving the wood, making it waterproof, or otherwise improving its characteristics and properties. While not limited thereto, the invention is especially concerned with the impregnation of wood with substances such as high melting point waxes and waxy compounds which are hard and non'- tacky under ordinary temperature conditions but which can be forced into the pores and tracheids of the wood under pressure while the impregnating substance is in a melted condition. For example, impregnations with Montan wax and with creosote mixed with Montan wax are no w used to a substantial extent in treating wood to pre-l serve it, increase its resistance to water, and to improve its characteristics in other respects. The present invention is especially concerned with the apparatus and methods .'of producing impregnations with materials of this general character.

As is well understood by those skilled in the art of wood impregnation, processes of this character which require the use of pressure to force the impregnating material into the inner strata of the wood, must be performed in a pressure cylinder. According tothe usual commercial practice the wood is loaded on trams which are run track and which'remain in the cylinder during the impregnating operation. Usually the cylinders are very large, are heavily 1 constructed, and they must be closed tightly during the entire pressure period. After the treatment has been completed the impregnating material is withdrawn from the cylinder, the cylinder is opened, the trams are run out into the open air, and the impregnated pieces are allowed to cool. Since impregnating materials of the type which are solid at normal tempera-tures set or harden rather quickly, and since there is usually a surplus of this material on the outer surfaces of the impregnated pieces, it is customary to run these pieces through a cleaning, operation for the purpose of removing this excess of material.

' Thismethod can be and is used very satis' factorily in the treatment of sizable pieces of wood. It is not' practical, however, to impregnatel somearticles by this process. For example, shingles. clapboards, and certain kinds of nooring, present peculiar problems because of the fact' that they are individually small, and are commonly handled in bunches. Ii. for example,

shingles or clapboards were to be treated in the manner above described, it would be necessary to break open the bunches at the conclusion of the process and to clean the individual shingles or clapboards, since otherwise the whole bunch 5 would be solidified into a solid mass bythe cool-- ing and setting of the impregnating medium.. Obviously, also, such pieces could not, as a practical matter, be handled in bulk in a pressure cylinder for similar reasons. In other words. 10 while the impregnatins can be made in this I manner, the labor cost involved in' them is so high, because of the nature of these articles, that it is not practical to impregnate them at the present time. In fact, no process or apparatus 15 is available at the present time, so far as we have been able to learn, with whichl pressure impregnations of shingles, clapboards, and other articles of a similar nature can be made on any price basis which gives even a hope of being 2,0 practical.

A careful consideration of the problem andthe various factors involved in it leads to the conclusion that articles of this kind must be-handled on some kind of a conveyor system so that, the 25 process can b e made substantially continuous. This conclusion, however, is of `little assistance 'when considered in connection with the fact that pressure impregnations must be performed in a closed cylinderfwherc both the material to be 30 impregnated and the treating liquid can be confined andthe desired pressure imposed on them. The present invention deals especially with the-problem presented by these conditions. It aims to devise both a thoroughly practical process and an apparatus withwhich it may be practiced for making pressure impregnations of shingles, clapboards and other small wooden parts and articles of a similar natureat a cost which will make 1t entirely feasible te lmpregnete these 4 articles on a commercial basis.

The nature of the invention will be readily understood from the followingidescription when read in connection with the accompanying drawings, and the novel features will be particularly pointed out inthe appended claims.

In the drawings.-

Figure 1 is a. perspective view of an apparatus constructedin accordance. with this invention; Fig. 2 is a side View of the apparatus shown in Fig. 1, the View being broken to indicate that it is much shortened in height; y

Fis. 3 is a diagrammatic view, partly in section.

of theI same apparatus, this view also being 55 broken to indicate that no attempt has been made to indicate proportions;

Fig. 4 is a plan view showing certain detailsof the conveyor; Y

Fig. 5 is a side elevation of a portion of the conveyor; and

Fig. 6 is a sectional view approximately on the line 6;-6, Fig. 4.

In impregnating shingles, clapboards, hard wood flooring, and the like, substantial pressures are required, such pressures running from, say, twenty-live pounds to the square inch to one hundred pounds, or even more. In addition, it is extremely desirable, as above indicated, that any method for impregnating articles of this character should be continuous. We have found that both of these objects can be realized, while still maintaining the expense of the treating plant within reasonable limits, by using an open ended treating cylinder arranged vertically, making it of such a height as Vto give the desiredrworking pressure, and handling the pieces to be treated on a continuous conveyor, the use of an open ended cylinder making it possible to employ a conveyor. The hydrostatic pressure of impregnating materials of the character above mentioned is in the neighborhood of .45 of a pound per foot of head. Consequently, ii the pieces which are to be treated pressure of fifty pounds per square inch, a vertical or inclined cylinder having a height of ap proximately one hundred and twenty feet would be required. Practical considerations very likely would also make it advisable to build the cylinder considerably in excess of this height so that a higher pressure would be available.

`Figs 1, 2 and 3 show a cylinder constructed in accordance with this invention, it being under stood that the term cylinder at all in its geometrical sense but rather in the functional sense in which it is employed in this industry to designate impregnating liquid is conilned and is placed under the desired pressure necessary to force it into the wood. In the particular arrangement shown the cylinder is given an approximately U- shaped form and is set on end. For convenience in installation advantage may be taken of an abrupt hillside, clii, or the like, if such is available, so that the expense of building a tower crv other supporting structure will be eliminated, or at least greatly reduced. The particular cylinder structure shown has two very'tall upwardly extending legs 2 and 3, joined at their lower ends by a larger horizontal section 4.

A conveyor, indicated diagrammatically at 5' in Fig. 3, is installed in the cylinder and is driven from an electric motor Bthrough suitable reduction gearing. The conveyor chain rims on suitable driving and guiding sprocket wheels l|, the

number of such wheels used necessarily depending upon the requirements of lndividualinstallations. Preferably the motor I is of the variable speed type so that the rate veyor chain i can be adjusted andcontrolled within le limits.

It will be observed that the conveyor includes an upper hcrizontaLreach'or run extending across a suitable platformt. It also includes a series of grippers Il, Figs. 4, 5 and 6, or equivalent devices for holding the shingles or other articles to be ted. vIn the particular construction shown inthe drawings the 'grippers Il are carried by eertainrof the conveyor unks, and each ilxed jaw a. Pig. 8, and

mincludesalcwer these articles successively will require a treating' is 'here used not' the container in which the.

of travel of the con- A an upper movable :law b pivoted to the lower jaw at c. the upper jaw also having a lower arm or extension d .which underlies the lower Jaw a and is pressed away from it by a coiled spring e. Normally the spring holds the gripper closed and therefore enables the gripper to hold a shingle S securely in it. As the conveyor travels across the platform 8 the arm d is engaged by the beveled edge of |a stationary cam plate i2, Figs. 3 and 5, which' swings this arm upwardly andthereby opens the gripper. The gripper is held in this open condition during the'entire period in-which it is moving across the plate i2, and during this interval, therefore, a shingle, clapboard, or other article to be impregnated, between the jaws of the gripper, holding it in this position while the gripper slides oil the right-hand end, Fig.-3, of the cam plate and closes on the article, thus grippingit securely. This operation is repeated as successive grippers move across the plate I2. The conveyor carries down the right-hand leg 2 of the cylinder and along the lower horizontal run of the conveyor which is located in the cylinder section I, and then carries them up .the other leg rof the cylinder and across the cam plate I2 again. On the way to the cam .plate each gripperfcarries its shingle `between a pair of revolving brushes "IL-I4, Fig. 3, which serve to remove excessive impregnating material from the surface of the shingle, this action being iacilitated by the fact that the gripper eng es the shingle at one edge and preferably 'near he thinner end so as to leave most of the body of the Y shingle Afully exposed for the action thereon of the brushes. A moment later the gripper is opened by its contact with the leading edge of the cam plate i2, whereupon the shingle is released and drops by gravity into an inclined chute I5 which carries it to the bunching machine, or to any other desired point of delivery. Obviously the shingles to be impregnated may be carried up to the platform 8 by a conveyor, or they may be delivered to the workmen in any other convenient manner.

It will be observed that as the shingles are carried down the long leg 2, Fig. 1, of the cylinder to the lower horizontal section sure on the portion of the impregnating liquid through which the shingle passes successively, gradually is increased until it reaches a maximum when the shingle arrives in the section I. It is maintained under this maximum pressure [for a length of timedetermined by the length .of this lower horizontal run of the conveyor and the conveyor speed. For' this reason it is very desirable to be able to control and adjust the conveyor speech as above described. Small or thin articles of wood, such as shingles, clapboards, and the like, do not, as a rule, require a long treating period penetration of the treating liquid into for a substantial depth. In thin pieces,A like shingles, a through and through impregnation is preferable, and this may also be desirable in certain grades of flooring, clapboards, and the like. However, this is not always n, and for many purposes a-penetration of in the neighborhood of .an eighth of ansinch is quite suincient. It should be understood, hcweventhat the degree of penetration obtained will depend'upon workman may place a.

in order to produce aV the wood I, the pres- Y pregnating bath is maintained, and other practical considerations well understood by those skilled in the art of wood impregnation. 'y

In making impregnations with Montan wax. creosote, and the like, it is desirable to maintain the treating bath at a temperature of between 220 and 250 F. Consequently, provision must be made for heating the bath in the cylinder. For this purpose a series of steam pipes I6 are located in thecylinder section 4, and additional steam pipes are located in the cylinder legs 2 and 3, or these legs may be. steam Jacketed as shown at-l 1, Fig. 3. Steam for this purpose is supplied from the boiler house I8, Fig. 1. It is also expected that the cylinder will be properly insulated to hold the heat radiation within reasonable limits.

The mixing and supply tanks required in connection with the cylinder, together with suitable pumps for forcing the impregnating liquid into the cylinder and controlling its height or hydrostatic head, may be substantially the same as those used with pressure cylinders of the common commercial types, it being understood that sound engineering principles and good treating plant practice should be followed in making any installation embodying this invention. e

It will be evident from the foregoing that small articles, such as shingles, clapboards, and the like, can be handled very economically and eificiently in this plant, that in it they can be given a pressure impregnating treatment just as effectually as in a pressure cylinder of the present commercial types in which the loads or charges must always be handled on a batch system. The inv vention, therefore, makes it feasible for the iirstl time, so far as we are aware, to impregnate -shingles, clapboards, hard wood flooring, and other small articles of wood o n a commercial basis.

While We have herein shown and described a typical embodiment of our invention and a preferred method of procedure, it will be understood that the invention may be embodied in other forms, and that the. steps of the process may be varied in some respects without departing .from the spirit or scope of the invention. For example, the treating cylinder may take a great variety of forms, and the particular design used in any given installation will necessarily vary with the practical requirements of the individual location. It is contemplated that the invention will be found useful in the impregnation of mine props and other mine timber which is used in short lengths, and that where so used the cylinder may take the form of a single upright section which may be conveniently located in an abandoned mine shaft, the conveyor running through the cylinder vjust as it does in the arrangement here illustrated, but having very short horizontal runs. l

Having thus described our invention, what we v desire to claim as new is:

l. 'I'hat improvement in methods of pressure impregnating articles of wood, and the like, which consists in passing said articles succcessively through a liquid impregnating bath in which a high pressure is maintained, holding said high pressure on a portion of said bath by maintaining a hydrostatic column of liquid in communication with said high pressure portion, and conveying said articles through said' column.

2. That improvement in methods of pressure impregnating articles ofwood, and the like, which articles successively through a liquid impregnating bath in which a 3. That improvement in methods of pressure` impregnating articlesof wood, and the like, which both Open to the atmosphere at their upper ends, whereby a high hydrostatic pressure is maintained on said high pressure portion of the bath,

and moving said articles downwardly through one of said columns into said high pressure portion, through vsaid portion of the bath, and upwardly out of said bath through the other column to theV atmosphere.

y JOSEPH R. COOLIDGE.`

JOHN H. MCCREADY. 

